Augmenting an original class with an augmenting class

ABSTRACT

An augmenting system for augmenting a program&#39;s original class with an augmenting class is provided. In some embodiments, the augmenting system receives a definition of an augmenting class that includes a data member. The augmenting system generates resolution code for the computer program. The resolution code is for accessing a reference to an original instance of the original class and providing a reference to a corresponding augmenting instance of the augmenting class. When processing a statement of the computer program that accesses the data member using the reference to the original instance, the augmenting system generates access code for the computer program. The access code uses the resolution code to retrieve the reference to the augmenting instance for the original instance and accesses the data member based on the retrieved reference to the augmenting instance.

BACKGROUND

Object-oriented programming (“OOP”) is based on objects that can containdata members and methods (also referred to as function members). Forexample, an object that represents a vehicle may contain data membersfor storing the brand and the model year of the vehicle and a method forprinting the values of the data members of the vehicles. The datamembers and methods for an object are specified by a class definition.For example, the class definition for a Vehicle class may be representedby the following pseudocode:

class Vehicle {  str brand;  int year;  void new( )  {   brand = null;  year = 0;  }  public void displayInfo( )  {   print (brand);   print(year)  }

This class definition includes two methods: new and displayInfo. The newmethod is a constructor that is invoked to initialize a Vehicle objectwhen the Vehicle object is instantiated (i.e., created). A Vehicleobject identified by the variable V may be instantiated and the datamembers and methods may be accessed as represented by the followingpseudocode:

Vehicle V = new Vehicle( ); V.year = 2016; V.model = “Ford”;V.displayInfo( ); nextyear = V.year + 1;

OOP also allows one class to inherit the data members and methods ofanother class. For example, there are many different types or kinds ofvehicles such as cars, trucks, and motorcycles. The vehicle types havesome attributes in common and some attributes that are specific to thevehicle type. The common attributes may be brand and year. Thecar-specific attributes may include whether the car is a convertible andhas a sun roof, and the truck-specific attributes may include maximumpayload and maximum towing capacity. Although separate classes can bedefined for each vehicle type, each class defining data members for thecommon attributes along with data members for the vehicle type-specificattributes, OOP inheritance allows the common attributes to be definedonce and then inherited by the vehicle type-specific classes. TheVehicle class defines the data members and methods that are common toall vehicles. The inheritance of the Vehicle class by a Car class, asubclass of the Vehicle class, is represented by the followingpseudocode:

class Car : Vehicle {  Boolean convertible;  public void new( )  {   super( );    convertible = true;  }  public void displayInfo ( )  {   super( );    print (convertible);  } }A Car object may be instantiated and accessed as represented by thefollowing pseudocode:

Car C = new Car( ); C.year = 2016; C.model = “Ford”; C.convertible =false; C.displayInfo( );The print method will print the following:

2016

Ford

hard top

Developers of application programs, such as customer relationshipmanagement (“CRM”) systems or enterprise resource planning (“ERP”)systems, allow users of the application programs (e.g., organizationsthat license the application programs) to customize the applicationprograms to meet their needs. For example, an application program mayinclude the Vehicle class, and a user may define the Car class, whichinherits the Vehicle class, to perform some car-specific processing.

In some cases, a user would like to add a new data member that is commonto all vehicles, such as color of the vehicle. The user could customizethe application program by modifying the Vehicle class to add the colordata member and modifying the application program to access the colordata member. The user would then need to recompile the applicationprogram including the source code of the modified Vehicle class. Thisrequires that the developer provide the source code to the user, whichthe developer may not want to do. Even if the developer did provide thesource code to the user, the modifying of the source code of the Vehicleclass by the user would present maintenance problems each time thedeveloper releases a modified version of the Vehicle class. In such acase, the user would need to reapply the customizations to theapplication program. As an alternative to modifying the Vehicle class,the user could modify each class that inherits the Vehicle class, suchas a Car class and a Truck class, to add the color data member. Asanother alternative, the user could create, for each subclass thatinherits from the Vehicle class, a class inherits that subclass andincludes the color data member. Although these alternatives do notrequire having access to and recompiling the source code of the Vehicleclass, the alternatives result in duplication of source code for eachclass that inherits from the Vehicle class, which is error-prone andincreases the cost of maintenance.

SUMMARY

An augmenting system for augmenting a computer program's original classwith an augmenting class is provided. In some embodiments, theaugmenting system receives a definition of an augmenting class thatincludes a data member. The augmenting system generates resolution codefor the computer program. The resolution code uses a reference to aninstance of the original class to provide a reference to a correspondinginstance of the augmenting class and to instantiate the correspondinginstance of the augmenting class if not already instantiated. Whenprocessing a statement of the computer program that accesses the datamember using the reference to the instance of the original class, theaugmenting system generates access code for the computer program. Theaccess code uses the resolution code to retrieve the reference to thecorresponding instance of the augmenting class and accesses the datamember using the retrieved reference to the instance of the augmentingclass.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a layout for an original class and anaugmenting class in some embodiments.

FIG. 2 is a diagram that illustrates two embodiments of the augmentingsystem.

FIG. 3 is a flow diagram that illustrates the processing of apre-compilation component in some embodiments.

FIG. 4 is a flow diagram that illustrates the processing of a resolutionfunction in some embodiments.

FIG. 5 is a block diagram that illustrates a computing system on whichthe augmenting system may be implemented.

DETAILED DESCRIPTION

A method and system for augmenting an original class with a data membernot defined in the definition of the original class is provided. In someembodiments, an augmenting system is provided that allows an augmentingclass with a data member to augment an original class so that the datamember can be accessed as if it were defined in the original class. Toaugment an original class, the source code of a computer programincludes a definition of an augmenting class that specifies the datamember. For example, an augmenting class may be defined as representedby the following pseudocode:

class AddColor {  str color; }

The source code also includes an augmentation statement that indicatesthat the original class is augmented with the augmenting class. Theaugmentation statement may not be part of the programming language, butrather may be considered metadata that informs a compiler or apre-compilation component that the augmenting class augments theoriginal class. For example, if the AddColor class augments the Vehicleclass, the augmentation statement may be as follows:

[AddColor augments Vehicle]

Alternatively, the augmentation statement may identify the originalclass explicitly and identify the augmenting class as the classimmediately following the augmentation statement as follows:

[Augments(Vehicle)] class AddColor {  str color; }

The source code also includes a statement to instantiate the originalclass. For example, the statement to instantiate an original instance ofthe original class may be represented by the following pseudocode:

Vehicle V = new Vehicle( );The source code includes a statement to access the data member of theaugmenting class using a reference to the original instance. Forexample, the statement to access the data member may be represented bythe following pseudocode:

V.color = “red”;

When the augmenting system processes a statement to access a data memberof the augmenting class using a reference to an original class, itgenerates code that instantiates an instance of the augmenting class(referred to as an “augmenting instance”) that corresponds to theoriginal instance if one has not already been instantiated. As a result,the augmenting system generates code to instantiate an augmentinginstance for each original instance whose reference was used to accessthe data member. The augmenting system then generates code to access thedata member of the augmenting instance, rather than accessing a datamember of the original instance.

In this way, the source code can be developed as if the data member weredefined in the original class itself except for the inclusion of theaugmenting class definition and the augmentation statement indicatingthat the augmenting class augments the original class. Moreover, sincethe original instance of an augmented original class is the same as anoriginal instance of a non-augmented original class, the computer codethat augments the original class can interoperate with computer codethat uses a non-augmented original class. For example, computer codethat augments the original class can pass a reference to an originalinstance of the augmented original class to a subroutine that has noknowledge of the augmentation and expects a reference to an originalinstance of the original class. Thus, a user of an application programdeveloped by another can generate custom code that augments an originalclass of the application program and that can interoperate with theapplication program without having to modify and/or recompile the sourcecode of the application program. Moreover, the original class can bemodified by the developer to, for example, add a new data member orchange an implementation of a function member. The developer can thenrelease a new assembly for the modified original class. The user can usethat new assembly with an assembly for the custom code to generate anexecutable of the application program without having to modify thecustom code. Similarly, the user can further modify the custom code andgenerate a new assembly that can be used with assembly provided by thedeveloper without having to reapply any customizations. Thus, theaugmentation system allows the application program and customizationsthat augment classes of the application program to be developed andmodified separately.

The augmenting system allows an original class to be augmented bymultiple augmenting classes. Each member of the augmenting classes canbe accessed as if it was actually defined by the original class. Asanother example, when a subclass inherits an original class that hasbeen augmented, the members of the augmenting class can be accessedusing a reference to an instance the subclass for non-static members anda reference to the subclass for static members. For example, if theVehicle class were an abstract that was augmented by the AddColor classand inherited by the Car class. The access of the color data member ofthe AddColor class can be represented by the following pseudocode:

Car C = new Car( ); C.brand = “Honda”; C.year = 2016; C.color = “red”;The last statement access the color data member of the augmenting classusing a reference to the instance of the Car class. Rather thanaugmenting the Vehicle class, the Car class could have been augmentedwith the AddColor class. In such a case, a Truck class that alsoinherits the Vehicle class would need to also be augmented with theAddColor class to access the color data member.

In some embodiments, the augmenting system may be implemented to processoriginal source code during a pre-compilation phase to generate amodified version of the source code or during compilation of theoriginal source code. If implemented during a pre-compilation phase, theaugmenting system may be implemented as a front-end to a compiler thatgenerates a modified version of the source code to support theaugmentation of original classes. The modified version can then becompiled by the compiler to generate assembly code that supports theaugmentation of the original classes. If implemented during compilationof the original source code, the augmenting system may be implemented asa modification to a compiler that generates assembly code that supportsthe augmentation of original classes. In either case, the augmentingsystem receives a definition of an augmenting class in the originalsource code that includes one or more data members or function members.For example, the augmenting class may be specified by the followingpseudocode:

[Augments(Vehicle)] class AddColor {  str color; }

In some embodiments, the augmenting system may add a static mapping datastructure to the augmenting class to map each original instance of theoriginal class to a corresponding augmenting instance of the augmentingclass. The mapping data structure is static in the sense that there isonly one occurrence of the mapping data structure that is shared by allaugmenting instances of the augmenting class. The mapping data structuremay be a table of entries, each of which stores a reference to anoriginal instance and a reference to the corresponding augmentinginstance.

The augmenting system may also add a resolution function to theaugmenting class that is passed a reference to an original instance andreturns a reference to the corresponding augmenting instance. If themapping data structure indicates that the corresponding augmentinginstance has not been instantiated, the resolution function instantiatesthe corresponding augmenting instance and updates the mapping datastructure. For example, the resolution function may search the mappingdata structure for an entry with a reference to the passed originalinstance. If an entry is found, the resolution function returns thereference to the corresponding augmenting instance. If an entry is notfound, the resolution function instantiates the corresponding augmentinginstance, adds an entry to the table for the passed original instanceand the newly instantiated augmenting instance, and returns thereference to the newly instantiated augmenting instance.

The augmenting system generates access code (e.g., assembly code) forsource code that accesses the data member using a reference to anoriginal instance. The access code invokes the resolution function ofthe augmenting class, passing a reference to the original instance, andaccesses the data member using the reference to the augmenting instancereturned by the resolution function. Thus, a computer program thataugments an original class can access a data member of the augmentingclass in the same way as a data member of the original class isaccessed.

The following example illustrates the access code generated by theaugmenting system. The augmenting class of the source code in thisexample is represented by the following pseudocode:

[Augments(Vehicle)] class AddColor { str color; }The augmentation system generates assembly code as if the augmentingclass were represented by the following pseudocode:

1. class AddColor 2. { 3.  Static Map<Vehicle, AddColor> BIAIMap; 4. str color; 5.  static int getAI(Vehicle BI) 6.  { 7.   if(BIAIMap.Contains(BI)) 8.    {return BIAIMap[BI]}; 9.   AddColor AI; 10.  AI = new AddColor( ); 11.   BIAIMap[BI] = AI; 12.   return AI; 13.  }The pseudocode in bold is a logical representation of the assembly codethat is generated by the augmentation system. Line 3 represents theadding of the mapping data structure to the augmenting class. Thebase-instance-to-augmenting-instance map (“BIAIMap”) is the mapping datastructure and is declared as static. Lines 5-12 represent the addedresolution function (“getAI”) that returns a reference to an augmentinginstance. The resolution function is passed a reference to an originalinstance (“BI”) and returns a reference to the corresponding augmentinginstance. Lines 7-8 determine whether BIAIMap contains an entry thatmaps the original instance to a corresponding augmenting instance. If anentry is found, then the reference to the augmenting instance in theentry is returned. If an entry is not found, lines 9-12 instantiate anaugmenting instance (“AI”), add an entry to BIAIMap, and return areference to the augmenting instance.

The augmenting system also generates access code for code that accessesa data member of an augmenting class. The source code that accesses datamembers of the original class and the augmenting class may berepresented by the following pseudocode:

{  Vehicle V = new Vehicle( );  V.brand = “Honda”;  V.year = 2016; V.color = “red”; }The access code may be logically represented by the followingpseudocode:

 {  Vehicle V = new Vehicle( );  V.brand = “Honda”;  V.year = 2016; AddColor::getAI(V).color = “red”; }The first three statements are the same because they instantiate theoriginal instance and access a data member of the original instance andnot in the augmenting instance. The last statement invokes the getAIfunction of the AddColor class, which is the augmenting class, and usesthe reference to the augmenting instance that is returned to set thecolor data member of the augmenting instance.

In some embodiments, the augmenting system may allow non-static functionmembers, static function members, and static data members to bespecified in an augmenting class. To support non-static functionmembers, the augmenting system may add an original instance data memberto the augmenting class. When the resolution function instantiates anaugmenting instance, the resolution function adds an entry to themapping data structure and also sets the original instance data memberto reference the original instance. The augmenting system also causesany access in the non-static function member to a data member of theoriginal instance to use the original instance data member to accessthat data member. Alternatively, rather than adding an original instancedata member to the augmenting class, the augmenting system may cause anyaccess in the non-static function member to invoke a resolution functionthat retrieves the reference to the original instance from the mappingdata structure. To support static members (i.e., static data members andstatic function members), the augmenting system causes each access to astatic member, which uses a reference to the augmenting class (e.g.,Vehicle::static_data_member or Vehicle::static_function_member( )), toaccess (i.e., invoke in the case of a function member) the static memberof the augmenting class.

FIG. 1 is a diagram illustrating a layout for an original class and anaugmenting class in some embodiments. The diagram represents the layoutafter execution of the following pseudo code.

1.  Vehicle V1 = new Vehicle( ); 2.  V1.brand = “Honda”; 3.  V1.color =“silver”; 4.  Vehicle V2 = new Vehicle( ); 5.  V2.color = “black”;6.  Vehicle V3 = new Vehicle( ); 7.  V3.year = 2015; 8.  Vehicle V4 =new Vehicle( ) 9.  V4.brand = “Honda”; 10. V4.color = “white”;11. V4.color = “red”;

The diagram includes the Vehicle layout 110 for the Vehicle class andthe AddColor layout 120 for the AddColor class. The Vehicle layoutincludes Vehicle instances V1-V4. The AddColor layout includes AddColorinstances AC1, AC2, and AC4 and a mapping data structure 130. When line1 is executed, Vehicle instance V1 is instantiated. When line 2 isexecuted, the brand data member of Vehicle instance V1 is set. When line3 is executed, the resolution function is executed passing a referenceto Vehicle instance V1. The resolution function determines that themapping data structure does not contain an entry for Vehicle instanceV1. Based on this determination, the resolution function instantiatesAddColor instance AC1, adds an entry 131 to the mapping data structurethat maps Vehicle instance V1 to AddColor instance AC1, and returns areference to the AddColor instance AC1. Upon return, the reference tothe AddColor instance AC1 is used to set the color data member ofAddColor instance AC1.

When line 4 is executed, Vehicle instance V2 is instantiated. When line5 is executed, the resolution function is executed passing a referenceto Vehicle instance V2. The resolution function determines that themapping data structure does not contain an entry for Vehicle instanceV2. Based on this determination, the resolution function instantiatesAddColor instance AC2, adds an entry 132 to the mapping data structurethat maps Vehicle instance V2 to AddColor instance AC2, and returns areference to the AddColor instance AC2. Upon return, the reference tothe AddColor instance AC2 is used to set the color data member ofAddColor instance AC2.

When line 6 is executed, Vehicle instance V3 is instantiated. When line7 is executed, the year data member of Vehicle instance V3 is set. Sincea statement that accesses the color data member of the AddColor class isnot present in the pseudo code, an AddColor instance corresponding toVehicle instance V3 is not instantiated. If a statement is eventuallyexecuted that sets or gets the color data member using a reference toVehicle instance V3, then an AddClass instance V3 would be instantiatedand an entry added to the mapping data structure.

When line 8 is executed, Vehicle instance V4 is instantiated. When line9 is executed, AddColor instance AC4 is instantiated and entry 134 isadded to the mapping data structure in the same way as discussed abovefor lines 3 and 6. When line 10 is executed, the resolution function isinvoked passing a reference to Vehicle instance V4. The resolutionfunction determines that the mapping data structure already contains anentry for Vehicle instance V4. So the resolution function returns areference to AddColor V4. Upon return, the reference to the AddColorinstance AC4 is used to set the color data member of AddColor instanceAC4.

FIG. 2 is a diagram that illustrates two embodiments of the augmentingsystem. The diagram illustrates a pre-compilation embodiment 210 and amodified compiler embodiment 220. In the pre-compilation embodiment, apre-compilation component 212 implements the augmenting system. Thepre-compilation component inputs source code 211 that includes anaugmenting class. The pre-compilation component generates a modifiedversion of the source code. In the modified version, the pre-compilationcomponent adds a mapping data structure and a resolution function to thedefinition of the augmenting class. The pre-compilation component alsomodifies each access to a data member of the augmenting class via areference to an original instance to use the resolution function. Thepre-compilation component outputs the modified version of the sourcecode 213, which is compiled by a compiler 214 to generate executable,assembly code, or object code 215. The compiler need not be modifiedwhen the pre-compilation component is used. In the modified compilerembodiment, the compiler has been modified to generate a modifiedcompiler 224. The modified compiler inputs source code 221 that includesan augmenting class and generates executable, assembly, or object code225 as if the augmenting class had included a mapping data structure anda resolution function and as if each access to a data member of theaugmenting class was via the resolution function.

FIG. 5 is a block diagram that illustrates a computing system on whichthe augmenting system may be implemented. A computing system 500 storessource code 510, compiler 520, and assembly code 530. The source codeincludes statements that define an augmenting class, indicate that theaugmenting class augments an original class, instantiate an originalinstance of the original class, and access a data member of theaugmenting class using a reference to the original instance. Thecompiler may be a conventional compiler that has been modified toinclude an implementation of an augmenting system 521. The compiler hasbeen modified to generate assembly code with a static mapping datastructure and a static resolution function added to the augmentingclass. The resolution function is passed a reference to an originalinstance (or a derived instance that inherits the original class) andreturns a reference to a corresponding augmenting instance of theaugmenting class. The compiler also generates assembly code for sourcecode statements that access the data member using a reference to theoriginal instance (or derived instance). The generated assembly codeinvokes the resolution function passing the reference to the originalinstance and using the returned reference to the augmenting instance toaccess the data member.

The computing systems on which the augmenting system may be implementedmay include a central processing unit, input devices, output devices(e.g., display devices and speakers), storage devices (e.g., memory anddisk drives), network interfaces, graphics processing units,accelerometers, cellular radio link interfaces, global positioningsystem devices, and so on. The input devices may include keyboards,pointing devices, touch screens, gesture recognition devices (e.g., forair gestures), head and eye tracking devices, microphones for voicerecognition, and so on. The computing systems may include servers of adata center, massively parallel systems, and so on. The computingsystems may access computer-readable media that includecomputer-readable storage media and data transmission media. Thecomputer-readable storage media are tangible storage means that do notinclude a transitory, propagating signal. Examples of computer-readablestorage media include memory such as primary memory, cache memory, andsecondary memory (e.g., DVD) and other storage. The computer-readablestorage media may have data recorded on them or may be encoded withcomputer-executable instructions or logic that implements the augmentingsystem. The data transmission media are used for transmitting data viatransitory, propagating signals or carrier waves (e.g.,electromagnetism) via a wired or wireless connection. The computingsystems may include a secure cryptoprocessor as part of a centralprocessing unit for generating and securely storing keys and forencrypting and decrypting deployment data using the keys.

The augmenting system may be described in the general context ofcomputer-executable instructions, such as program modules andcomponents, executed by one or more computers, processors, or otherdevices. Generally, program modules or components include routines,programs, objects, data structures, and so on that perform particulartasks or implement particular data types. Typically, the functionalityof the program modules may be combined or distributed as desired invarious examples. Aspects of the augmenting system may be implemented inhardware using, for example, an application-specific integrated circuit(ASIC).

FIG. 3 is a flow diagram that illustrates the processing of apre-compilation component in some embodiments. A pre-compilationcomponent 300 inputs source code that includes an augmenting class andoutputs modified source code. In block 301, the component retrieves anaugmentation statement from the source code. In block 302, the componentretrieves the definition of the corresponding augmenting class from thesource code. In block 303, the component adds a definition of a mappingdata structure to the augmenting class definition. In block 304, thecomponent adds a resolution function to the augmenting class definition.In blocks 305-307, the component loops modifying each access to a datamember of the augmenting class via a reference to the original instanceto use the resolution function. The component then outputs the modifiedsource code and completes.

FIG. 4 is a flow diagram that illustrates the processing of a resolutionfunction in some embodiments. A resolution function 400, named getAI, ispassed a reference to an original instance and returns a reference to acorresponding augmenting instance. In decision block 401, the functiondetermines whether an entry for the original instance is in the mappingdata structure. If so, the function retrieves the reference to thecorresponding augmenting instance from the entry in block 402 and thenreturns the reference. If not, the function continues at block 403. Inblock 403, the function instantiates a new augmenting instance. In block404, the function adds to the mapping data structure an entry that mapsthe original instance to the augmenting instance and then returns thereference to the augmenting instance.

The following paragraphs describe various embodiments of aspects of theaugmenting system. An implementation of the augmenting system may employany combination of the embodiments. The processing described below maybe performed by a computing device with a processor that executescomputer-executable instructions stored on a computer-readable storagemedium that implements the augmenting system.

In some embodiments, a computer-readable storage medium that stores acomputer program that augments an original class with an augmentingclass is provided. The computer program comprising statements thatdefine the augmenting class wherein the augmenting class includes a datamember. The statements indicate that the augmenting class augments theoriginal class. The statements instantiate an original instance of theoriginal class. The statements access the data member of the augmentingclass using a reference to the original instance. In some embodiments,the statements that define, instantiate, and access are statements of aprogramming language. In some embodiments, the statement that indicatesis not part of the programming language. In some embodiments, thestatement that indicates is metadata of the computer program. In someembodiments, the metadata indicates to a compiler that the augmentingclass augments the original class. In some embodiments, the programminglanguage is object-oriented. In some embodiments, the statements do notinclude a statement to instantiate the augmenting class.

In some embodiments, a method performed by a computing device foraugmenting an original class with an augmenting class is provided. Themethod receives a definition of the augmenting class wherein theaugmenting class includes a data member. The method adds a staticmapping data structure to the augmenting class to map each originalinstance of the original class to a corresponding augmenting instance ofthe augmenting class. The method adds a resolution function to theaugmenting class that is passed a reference to the original instance andreturns a reference to the corresponding augmenting instance of theaugmenting class. The resolution function is adapted to, if the mappingdata structure indicates that the corresponding augmenting instance hasnot been instantiated, instantiate the corresponding augmenting instanceand update the mapping data structure to indicate that the correspondingaugmenting instance has been instantiated. The method generates code forcode that accesses the data member using a reference to an originalinstance wherein the generated code invokes the resolution function ofthe augmenting class passing the original instance and accessing thedata member using a reference to the augmenting instance returned by theresolution function. In some embodiments, the definition of theaugmenting class and the code that accesses the data member arespecified using an object-oriented programming language. In someembodiments, the mapping data structure, for each original instance witha corresponding augmenting instance, contains an entry with a referenceto the original instance and a reference to the corresponding augmentinginstance. In some embodiments, the resolution function is furtheradapted to, if the mapping data structure indicates that thecorresponding augmenting instance has been instantiated, retrieve fromthe mapping data structure a reference to the corresponding augmentinginstance. In some embodiments, the method receives metadata indicatingthat the augmenting class augments the original class. In someembodiments, the adding of the static mapping data structure, the addingof the resolution function, and the modifying are performed duringcompilation of a computer program. In some embodiments, the computerprogram includes statements that define the augmenting class, indicatethat the augmenting class augments the original class, instantiate anoriginal instance of the original class, and access the data member ofthe augmenting class using a reference to the original instance.

In some embodiments, a computing system for compiling a computer programwith an original class that is augmented with an augmenting class isprovided. The computing system includes a computer-readable storagemedium storing instructions and a processor for executing theinstructions stored in the computer-readable storage medium. Theinstructions receive a definition of the augmenting class where theaugmenting class includes a data member. The instructions generateresolution code for the computer program. The resolution code is foraccessing a reference to an original instance of the original class andproviding a reference to a corresponding augmenting instance of theaugmenting class. The instructions, when compiling a statement of thecomputer program that accesses the data member using the reference tothe original instance, generate access code for the computer program.The access code for using the resolution code to use a reference to theoriginal instance to retrieve the reference to the augmenting instanceand for accessing the data member based on the retrieved reference. Insome embodiments, multiple augmenting classes augment the originalclass. In some embodiments, the resolution code is adapted to access amapping data structure that, for each original instance with acorresponding augmenting instance, contains an entry with a reference tothe original instance and a reference to the corresponding augmentinginstance. In some embodiments, the resolution code is a function that isadapted to, when a mapping data structure indicates that thecorresponding augmenting instance has not been instantiated, instantiatethe augmenting instance, add a mapping from the original instance to theaugmenting instance, and provide the reference to the augmentinginstance. The resolution code is further adapted to, when the mappingdata structure indicates that the corresponding augmenting instance hasbeen instantiated, retrieve from the mapping data structure the mappingfrom the original instance to the augmenting instance and provide thereference to the augmenting instance. In some embodiments, theinstructions further receive metadata indicating that the augmentingclass augments the original class.

In some embodiments, a method performed by a computing system forprocessing a computer program with an original class that is augmentedwith an augmenting class is provided. The method receives a definitionof the augmenting class where the augmenting class includes a datamember. The method, when processing a statement of the computer programthat accesses the data member using a reference to an original instanceof the original class, generates access code for the computer program.The access code is adapted to instantiate an augmenting instance of theaugmenting class and access the data member of the augmenting instance.In some embodiments, the static member is a data member. In someembodiments, the static member is a function member.

In some embodiments, a computer-readable storage medium storing acomputer program that augments an original class with an augmentingclass is provided. The computer program includes statements. Thestatements define the augmenting class where the augmenting classincluding a data member. The statements indicate that the augmentingclass augments the original class. The statements instantiate a derivedinstance of a derived class that inherits the original class. Thestatements access the data member of the augmenting class using areference to the derived instance.

Although the subject matter has been described in language specific tostructural features and/or acts, it is to be understood that the subjectmatter defined in the appended claims is not necessarily limited to thespecific features or acts described above. Rather, the specific featuresand acts described above are disclosed as example forms of implementingthe claims. Accordingly, the invention is not limited except as by theappended claims.

1-24. (canceled)
 25. A computer-readable storage medium storing acomputer program including statements which, when executed by aprocessor, cause the processor to: define an augmenting class foraugmenting an original class with the augmenting class, the augmentingclass including a data member; indicate that the augmenting classaugments the original class; instantiate an original instance of theoriginal class; and access the data member of the augmenting class usinga reference to the original instance.
 26. The computer-readable storagemedium of claim 25, wherein the statements that cause the processor todefine, instantiate, and access are statements of a programminglanguage.
 27. The computer-readable storage medium of claim 26, whereinthe statements that cause the processor to indicate that the augmentingclass augments the original class are not part of the programminglanguage.
 28. The computer-readable storage medium of claim 26, whereinthe statements that cause the processor to indicate that the augmentingclass augments the original class are metadata of a computer program.29. The computer-readable storage medium of claim 28, wherein themetadata indicates to a compiler that the augmenting class augments theoriginal class.
 30. The computer-readable storage medium of claim 26,wherein the programming language is object-oriented.
 31. Thecomputer-readable storage medium of claim 25, wherein the statements donot include a statement to instantiate the augmenting class.
 32. Thecomputer-readable storage medium of claim 25, wherein an indication thatthe augmenting class augments the original class includes: anaugmentation statement that specifies the augmenting class for theoriginal class, and a definition of the augmenting class that specifiesthe data member.
 33. The computer-readable storage medium of claim 32,wherein the statements are further to cause the processor to: responsiveto indicating that the augmenting class augments the original class, adda mapping data structure to the augmenting class in a source code, themapping data structure to map the original instance of the originalclass to a corresponding augmenting instance of the augmenting class.34. The computer-readable storage medium of claim 33, wherein thestatements are further to cause the processor to: add a resolutionfunction to the augmenting class in the source code, the resolutionfunction to cause the processor to: receive the reference to theoriginal instance; return a reference to a corresponding augmentinginstance of the augmenting class; determine that the mapping datastructure indicates that the corresponding augmenting instance has notbeen instantiated; instantiate the corresponding augmenting instance inresponse to determining that the mapping data structure indicates thatthe corresponding augmenting instance has not been instantiated; andupdate the mapping data structure to indicate that the correspondingaugmenting instance has been instantiated.
 35. The computer-readablestorage medium of claim 34, wherein the statements that cause theprocessor to access the data member using the reference to the originalinstance further cause the processor to access the data member using thereference to the corresponding augmenting instance returned by theresolution function.
 36. A computing system comprising: a processor; anda computer-readable storage medium storing a computer program thataugments an original class with an augmenting class, the computerprogram comprising statements that when executed by the processor, causethe processor to: define the augmenting class for augmenting theoriginal class with the augmenting class, the augmenting class includinga data member; indicate that the augmenting class augments the originalclass; instantiate an original instance of the original class; andaccess the data member of the augmenting class using a reference to theoriginal instance.
 37. The computing system of claim 36, wherein thestatements that cause the processor to define, instantiate, and accessare statements of a programming language.
 38. The computing system ofclaim 37, wherein the statements that cause the processor to indicatethat the augmenting class augments the original class is metadata of acomputer program that is not part of the programming language, whereinthe metadata indicates to a compiler that the augmenting class augmentsthe original class.
 39. The computing system of claim 37, wherein theprogramming language is object-oriented.
 40. The computing system ofclaim 36, wherein an indication that the augmenting class augments theoriginal class includes an augmentation statement that specifies theaugmenting class for the original class, and a definition of theaugmenting class that specifies the data member.
 41. The computingsystem of claim 40, wherein the statements are further to cause theprocessor to: responsive to the indication that the augmenting classaugments the original class, add a mapping data structure to theaugmenting class in a source code, the mapping data structure to map theoriginal instance of the original class to a corresponding augmentinginstance of the augmenting class.
 42. The computing system of claim 41,wherein the statements are further to cause the processor to: add aresolution function to the augmenting class in the source code, theresolution function to cause the processor to: receive the reference tothe original instance; return a reference to the correspondingaugmenting instance of the augmenting class; determine that the mappingdata structure indicates that the corresponding augmenting instance hasnot been instantiated; instantiate the corresponding augmenting instancein response to determining that the mapping data structure indicatesthat the corresponding augmenting instance has not been instantiated;and update the mapping data structure to indicate that the correspondingaugmenting instance has been instantiated.
 43. The computing system ofclaim 42, wherein the statements that cause the processor to access thedata member using the reference to the original instance further causethe processor to access the data member using the reference to thecorresponding augmenting instance returned by the resolution function.44. A method performed by a computing system, the method comprising:defining, by a processor, an augmenting class, the augmenting classincluding a data member; indicating, by the processor, that theaugmenting class augments an original class; instantiating, by theprocessor, a derived instance of a derived class that inherits theoriginal class; and accessing, by the processor, the data member of theaugmenting class using a reference to the derived instance.